CBSE: NCERT Solutions for Class 12 Chemistry Chapter 4 Chemical Kinetics MCQ’s with Answers
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NCERT Physics MCQs for Class 12 Chemistry Chapter 4 Chemical Kinetics Question and Answers PDF Q1.The rate of a reaction is primarily determined by the slowest step. This step is called (a) rate determining step (b) activation step (c) reaction rate step (d) none of these. Answer: (a) rate determining step Q2. The reaction of high molecularity are rare because (a) Many body collisions have a low probability. (b) Many body collisions are not favoured energetically. (c) Activation energy of many body collisions is very large (d) Very high concentration is required for such reactions. Answer: (a) Many body collisions have a low probability. Q3. For a chemical reaction A → B, it is found that the rate of the reaction quardruples when the concentration of A is doubled. The rate expression for the reaction is, rate = k [A]n where the value of n is (a) 1 (b) 2 (c) 0 (d) 3 Answer: (b) 2 Q4. On increasing the temperature of the reacting system by 10° the rate of reaction almost becomes double. The most appropriate reason for this is that (a) Activation energy decreases by increases of temperature (b) The fraction of molecules having threshold energy increases (c) Collision frequency increases (d) The value of threshold energy decreases. Answer: (b) The fraction of molecules having threshold energy increases Q5. A zero order reaction A → Products, has rate constant 10-2 mole L-1 s-1. If a process is started with 10 moles of A in a one litre vessel, the number of moles of reactant after 10 minutes will be (a) 10 (b) 5 (c) 6 (d) 4. Answer: (d) 4. Q6.Rate constant of a reaction depends upon (a) Temperature (b) time (c) initial concentration (d) none Answer: (a) Temperature Q7. DDT on exposure to water decomposes. Half-life = 10 years. How much time will it take for its 90% decomposition? (a) 50 years (b) 70 years (c) 500 years (d) 700 years. Answer: (b) 70 years Q8. The rate of a first order reaction is 1.5 × 10-2 mol L-1 min-1 at 0.5 M concentration of the reactant. The half-life of the reaction is (a) 0.383 mm (b) 23.1mm (c) 8.73 mm (d) 7.53 mm Answer: (b) 23.1mm Q9. The rate equation for the reaction 2A + B → C is found to be: rate = k [A] [B]. The correct statement inxelation to this reaction is that the (a) unit of R must be s-1 (b) t1/2 is constant (c) rate of formation of C is twice the rate of disappearance of A. (d) value of k is independent of the initial concentration of A and B. Answer: (d) value of k is independent of the initial concentration of A and B. Q10.The reaction 2 SO2 (g) + O2 (g) ⇌ SO3 (g) is carried out in 1 dm³ vessel and 2 dm³ vessel separately. The ratio of the reaction velocities will be (a) 1 : 8 (b) 1 : 4 (c) 4 : 1 (d) 8 : 1 Answer: (d) 8 : 1 Q11.Which of the following statements is not correct for order of a reaction? (a) Order of a reaction can be determined experimentally. (b) It is the sum of the powers of concentration terms in the rate law expression. (c) It does not necessarily depend on the stoichiometric coefficients. (d) Order of a reaction cannot be fractional. Answer: (d) Order of a reaction cannot be fractional. Q12. t1/4 can be taken as the time taken for the concentration of a reactant to drop to 3/4 of its initial value. If the rate constant for a first order reaction is K, then t1/4 can be written as (a) 0.10/K (b) 0.29/K (c) 0.69/K (d) 0.73/K Answer: (b) 0.29/K Q13. Collision Theory is applicable to (a) First order reactions (b) Zero order reactions (c) Biomolecular reactions (d) Intramolecular reactions. Answer: (c) Biomolecular reactions Q14. The reaction A → B follows first order kinetics. The time taken for 0.8 mole of A to produce 0.6 mole of B is 1 hour. What is the time taken for conversion of 0.9 mole of A to produce 0.675 mole of B? (a) 1 hour (b) 0.5 hour (c) 0.25 hour (d) 2 hours. Answer: (a) 1 hour Q15. The rate of reaction between two reactants A and B decreases by a factor of 4 if the concentration of reactant B is doubled. The order of this reaction with respect to the reactant B is (a) 2 (b) -1 (c) 1 (d) -2 Answer: (d) -2 Q16.For reaction aA → xP, when [A] = 2.2 mM the rate was found to be 2.4 mMs-1. On reducing the concentration of A to half, the rate changes to 0.6 mMs-1. The order of reaction with respect to A is (a) 1.5 (b) 2.0 (c) 2.5 (d) 3.0 Answer: (b) 2.0 Q17. The half-lives of two samples are 0.1 and 0.4 second. Their respective concentrations are 200 and 50 respectively. What is the order of the reaction? (a) 0 (b) 2 (c) 1 (d) 4 Answer: (b) 2 Q18.In a first order reaction, the concentration of the reactant decreases from 800 mol/dm³ to 50 mol/dm³ in 2 × 104 sec. The rate constant for the reaction in sec-1 (a) 2 × 104 (b) 3.45 × 10-5 (c) 1.386 × 10-4 (d) 2 × 10-4 Answer: (c) 1.386 × 10-4 Q19.For the reaction A + B → C + D, doubling the concentration ofboth the reactants increases the reaction rate by 8 times and doubling the concentration of only B simply doubles the reaction rate. The rate law is given as (a) r = k[A] [B] (b) r = k [A] [B]² (c) r – k [A]² [B] (d) r = k [A] [B] Answer: (c) r – k [A]² [B] Q20.In Arrhenius plpt, intercept is equal to (a) -Ea/R (b) ln A (c) ln k (d) log10 a Answer:(b) ln A Q21.When a biochemical reaction is carried out in laboratory from outside of human body in absence of enzyme, then the rate of reaction obtained is 10-6 times, then activation energy of reaction in presence of enzyme is: (a) 6/RT (b) Pis required (c) Different from Ea obtained in the laboratory (d) Cannot, say anything Answer: (c) Different from Ea obtained in the laboratory Q22.If ‘I’ is the intensity of absorbed light and ‘C’ is the concentration of AB for the photochemical process AB + hv → AB+, the rate of formation of AB* is directly proportional to: (a) C (b) l (c) l2 (d) Cl. Answer: (b) l Q23.The rate constant for the reaction 2N2O5 → 4NO2 + O2 is 3.0 × 10-5 sec-1. If the rate is 2.40 × 10-5 mol litre-1 sec-1, then the concentration of N2O5 (in mol litre-1) is: (a) 1.4 (b) 1.2 (c) 0.04 (d) 0.8 Answer: (d) 0.8 Q24.The rate of a reaction is 1.209 × 10-4L² mol-2s-1. The order of the reaction is: (a) zero (b) first (c) second (d) third Answer: (d) third Q25.A catalyst increases the rate of a reaction by (a) increasing threshold energy (b) increasing activation energy (c) activating the reactants (d) lowering activation energy Answer: (d) lowering activation energy We hope that the given NCERT MCQ Questions for Class 12 Chemistry Chapter 4 Chemical Kinetics with Answers MCQ Chapter 4 Chemical Kinetics Free Pdf download will help you in gaining knowledge on the subject.